For shitcoin and memecoin it is like gambling because there is nothing to analyze or do research you buy a coin and then wait to win or lose while with bitcoin and strong coins you need to have the experience and do deep research and technical and fundamental analysis to know when to buy and when to sell.
The only difference between investing/trading and gambling is knowledge, nothing more, nothing less. If you have no knowledge but are greedy and rush to trade then even if you trade bitcoin or top altcoins as you said, you will still lose and it is no different than you are gambling. Because if we have knowledge, most of us will tend to stay away from scam shitcoins, we won't waste our time on it, only ignorant people rush in with the hope of getting rich quickly.
Also what are Doge, Shib or Pepe called? To me they are memecoins but they are all in the top 10 to top 20 on CMC. Many people can also make profits and even get rich from them, so I don't think all memecoins are bad.